CN101531444B - Sewage recycling process for combination of biological rapid filtration and slow filtration - Google Patents

Abstract

The invention relates to a biological fast-filtration and slow-filtration combined sewage recycling process, which belongs to the field of sewage treatment. Including the biological fast filtration and slow filtration steps, the influent water enters the biological fast filter and the slow filter in sequence, and through the combination of the biological fast filtration and the slow filtration, it is used to realize the remaining organic matter, ammonia nitrogen, total nitrogen, suspended solids, turbidity in the secondary effluent. Removal of brightness, color and odor. The sewage after biological fast filtration and slow filtration becomes qualified reuse water after disinfection, which can be used as municipal water for greening or flushing toilets. The biological fast filtration and slow filtration combined sewage recycling process of the present invention introduces the slow filtration into the sewage recycling process and combines it with the biological fast filtration to take advantage of each, thereby becoming an economical and efficient sewage recycling process.

Description

Bio-Fast Filtration and Slow Filtration Combined Sewage Reuse Process

technical field

The invention relates to a bio-fast filtration and slow filtration combined sewage recycling process, which belongs to the field of sewage treatment and is a process for advanced treatment and reuse of sewage.

Background technique

my country is a country that lacks water resources, and water pollution is also very serious. The water crisis has not been effectively curbed so far, and there is a tendency of further aggravation. Sewage reuse not only opens up new water sources, but also reduces sewage discharge, which can serve the dual purposes of alleviating water shortages and restoring a good water environment. This has become the consensus of the international water treatment and water resources circles.

After the sewage is regenerated, it can be used for farmland irrigation, industrial cooling water replenishment, and can also be used for landscaping, road spraying, toilet flushing, car washing and other urban miscellaneous purposes. According to different reuse purposes, the reused water must meet the corresponding water quality standards.

At present, with the continuous development of the economy and the continuous improvement of people's living standards, in addition to the traditional indicators of organic matter, ammonia nitrogen and turbidity in recycled water, people have also put forward higher requirements for the sensory indicators of reclaimed water. Such as the odor and color of reclaimed water that are generally concerned at present.

The current traditional sewage reuse process is coagulation sedimentation (clarification) + filtration + disinfection. The process has low investment and operating costs, and has a good removal effect on turbidity and suspended solids, but has limited removal effects on organic matter, ammonia nitrogen and other nutrients, especially color and odor, which are almost impossible to remove.

In order to further improve water quality, advanced oxidation technologies such as activated carbon adsorption, membrane technology and ozone have been introduced into the field of sewage reuse. The outstanding advantage of this type of process is that it can remove trace organic matter, odor and color in part of the water, but there are also disadvantages. For example, some advanced oxidation processes not only consume chemical substances and energy, but may also generate some more toxic intermediate products. Membrane method is a promising treatment method, but the problem of high price, complicated pretreatment and membrane fouling has not been solved yet. And the concentrated water produced by the membrane method must be further treated. The removal efficiency of the adsorption method (activated carbon) is very good and has a broad spectrum. The disadvantage of the adsorption method is that the adsorbent has a limited adsorption capacity and needs to be constantly replaced. In addition, the saturated adsorbent needs further treatment, otherwise it will easily cause secondary pollution.

In summary, there is an urgent need to develop efficient and low-consumption wastewater reuse processes.

In recent years, biological rapid filtration processes such as biological aerated filter have been gradually applied to sewage reuse. Due to the use of large particle size filter material and thicker filter bed, the secondary effluent of the sewage plant can directly enter the biological aerated filter without coagulation and sedimentation. Due to the enhanced biological action, the biological aerated filter can not only remove turbidity, but also effectively remove ammonia nitrogen and conventional organic substances. In the field of sewage reuse, biological aerated filters have gradually become a substitute for traditional fast filters. Many newly designed reclaimed water plants in China have adopted the biological aerated filter process.

Compared with the traditional process, although the biological aerated filter improves the quality of reclaimed water and simplifies the production process of reclaimed water, it has limited removal effect on odor and color.

Slow filtration is an ancient process with a history of more than 200 years. Slow filtration is a type of biological filtration in which a viscous film (schmutzdecke) is formed on the surface of a well-operated slow filter. A large number of bacteria, fungi, algae and even micro-animals will grow in the slow filter tank and form a complete ecosystem. Relying on the joint action of these microorganisms, slow filtration has a good ability to remove organic matter, and can better remove odor and color, and at the same time, the removal rate of bacteria and viruses can reach more than 90%.

Due to the disadvantage of occupying a large area, the slow filtration process was once neglected and replaced by fast filtration. Because of its good ability to remove organic matter, especially trace organic matter, bacteria, and viruses, slow filtration has gained attention again in today's deteriorating water environment. The slow filtration process is widely used in current European waterworks and is considered to be an effective means of removing trace substances in water. For a long time, slow filters have also been used for denitrification and advanced treatment of sewage.

Contents of the invention

Based on the analysis of the current status of the existing domestic and foreign sewage recycling technologies, the present invention proposes a new recycling process, especially a biological fast-filtration and slow-filtration combined sewage recycling process. The present invention introduces the slow filtration into the sewage recycling process, and combines it with the biological fast filtration, and takes advantage of each, so that the combination becomes an economical and efficient sewage recycling process.

Technical scheme of the present invention is as follows:

The present invention is a biological fast filtration and slow filtration combined sewage recycling process, including biological fast filtration and slow filtration steps. The specific steps for the removal of total nitrogen, suspended solids, turbidity, color and odor are as follows: First, the effluent after the secondary treatment of sewage is used as the influent, and the influent directly enters the biological fast filter, and the biological fast filter simultaneously With biological function and physical filtration, it is used to remove organic matter, ammonia nitrogen and suspended solids in the effluent of secondary sewage treatment; then, the effluent from the biological fast filter enters the slow filter again, and the slow filter relies on a layer of viscosity on the surface of the filter material The biological function of the membrane further removes the residual organic matter, ammonia nitrogen, suspended solids and turbidity substances in the effluent of the biological fast filter. The purpose of effluent water quality; the sewage after biological fast filtration and slow filtration, after disinfection, becomes qualified reuse water, which is used as municipal miscellaneous water for greening or flushing toilets.

The described biological fast-filtration and slow-filtration combined sewage recycling process is characterized in that: the activated sludge process or the biofilm process is used for the secondary treatment of sewage, and it is determined whether the secondary treatment of sewage depends on the purpose of the reused water Carry out nitrogen and phosphorus removal.

Described a kind of biological rapid filtration and slow filtration combined sewage recycling process is characterized in that: the biological filter in the biological filtration step is a common fast filter with enhanced biological action, wherein the biological action is strengthened by the following means : According to the raw water quality, add an aeration device or pre-aeration at the bottom of the filter, adjust the backwash strategy of the filter to reduce the damage to the biofilm on the filter material by backwash, and do not add disinfectant to the incoming water of the biological fast filter .

Said biological fast filtration and slow filtration combined sewage recycling process is characterized in that: according to the filter material, the thickness of the filter bed and the water quality of the influent, the filtration rate of the biological fast filter is controlled between 0.5-10m/h.

The above-mentioned combined sewage reuse process of biological fast filtration and slow filtration is characterized in that: the biological fast filter is an aerated biological filter, a biologically active filter or an aerobic filter.

The biological fast filtration and slow filtration combined sewage recycling process is characterized in that: the slow filter has biological and filtering functions, and the slow filter does not need backwashing, but requires periodic sand scraping.

The biological fast-filtration and slow-filtration combined sewage recycling process is characterized in that: according to the influent water quality, the filtration rate of the slow filter is controlled between 0.1-0.5m/h.

The said biological fast filtration and slow filtration combined sewage recycling process is characterized in that: the slowly filtered water is sterilized by chlorine gas, ultraviolet rays, chlorine dioxide or ozone disinfection methods.

The biological fast filtration and slow filtration combined sewage reuse process of the present invention combines the biological fast filtration (biological aerated filter) and the slow filtration, utilizes the biological fast filtration to remove the turbidity and suspended matter of the secondary effluent of the sewage plant, and further Remove organic matter and nitrated ammonia nitrogen from water. At the same time, high-quality water is provided for the subsequent slow filtration to reduce and avoid the clogging of the slow filtration. Use slow filtration to remove odor and color, and further remove residual organic matter, ammonia nitrogen, suspended solids and turbidity in the fast-filtered water, so as to improve the sensory perception of reclaimed water and ensure the safety of reclaimed water. At the same time, the good removal effect of slow filtration on bacteria and viruses can also reduce the subsequent disinfection load and improve the disinfection effect.

Description of drawings

Fig. 1 is a process flow diagram of the biological fast filtration and slow filtration combined sewage reuse process of the present invention.

Detailed ways

As shown in Fig. 1, the specific embodiment of the present invention is as follows.

The biological fast filtration and slow filtration combined sewage recycling process includes biological fast filtration and slow filtration steps. The specific steps for the removal of chromaticity and odor are as follows: First, the effluent after the secondary treatment of sewage is used as the influent, and the influent directly enters the biological fast filter. The biological fast filter has both biological and physical filtration functions. To remove organic matter, ammonia nitrogen, suspended solids and turbidity substances in the effluent of the secondary sewage treatment; then, the effluent of the biological fast filter enters the slow filter again, and the slow filter relies on the biological action of a layer of viscous film on the surface of the filter material to further Remove the residual organic matter, ammonia nitrogen and suspended solids in the effluent of the biological fast filter. At the same time, use the good biological filtration performance of the slow filter to remove the chroma, odor and bacteria in the water, so as to improve the water quality of the effluent; The sewage after filtration and slow filtration becomes qualified reuse water after disinfection, which can be used as municipal miscellaneous water for greening or flushing toilets.

Among them, the secondary treatment of sewage can adopt processes such as activated sludge method and biofilm method. Whether secondary treatment requires nitrogen and phosphorus removal depends on the use of reused water.

The biological filter in the biological filtration step is an ordinary fast filter with enhanced biological action, and the biological action can be enhanced by the following ways: according to the raw water quality, add an aeration device or pre-aeration at the bottom of the filter, adjust the filter The backwashing strategy reduces the destructive effect of backwashing on the biofilm on the filter material, and does not add chlorine and other disinfectants to the incoming water of the biological fast filter. According to the filter material, the thickness of the filter bed and the quality of the influent water, the filtration rate of the biological fast filter is controlled between 0.5 and 10m/h. The biological fast filter can be an aerated biological filter, a biologically active filter or an aerobic (aerobic) filter.

The slow filter in the above-mentioned combined sewage reuse process of biological fast filtration and slow filtration has biological function and filtering function, and the slow filter does not need backwashing, but requires periodic sand scraping. According to the influent water quality, the filtration rate of the slow filter is controlled between 0.1 and 0.5m/h.

After the effluent of the slow filter is disinfected, it becomes qualified reuse water. The process of the present invention does not limit the disinfection method. That is, after the water is slowly filtered out, conventional chlorine, ultraviolet, chlorine dioxide, ozone and other disinfectants can be used. The dosage of disinfectant should be determined through experiments.

The beneficial effects of the present invention can be verified by the following experimental results.

A combined system of fast and slow filtration was established. Two DN100 plexiglass tubes were used to simulate the biological fast filter and the slow filter respectively. The main parameters of the two simulated filters are shown in Table 1.

Table 1 Main parameters of biological fast filter and slow filter combined system

The combined process uses the effluent of a set of domestic sewage secondary treatment device as the influent. The domestic sewage mainly comes from a residential area. The secondary treatment adopts ordinary SBR process, without considering the removal of nitrogen and phosphorus. The secondary effluent first enters the bottom of the biological rapid filter, and then flows upward through the filter bed at a filtration rate of 1m/h. In order to provide enough oxygen for the microorganisms in the filter bed, a set of aeration device is installed at the bottom of the biological fast filter, and the air-water ratio is 3:1. After the biological fast filter, the water flows downwards and then enters the slow filter, and the water is discharged after passing through the slow filter at a filtration rate of 0.1m/h.

The combined system adopts the start-up method of natural film formation, and then enters a stable operation period. Table 2 shows the average experimental results of the combined system in the winter water temperature period (12°C-15°C). It can be seen from Table 2 that the combination process of biological fast filtration and slow filtration has a good removal effect on organic matter (COD) and turbidity. There is also better removal of chroma. Although the removal rate of ammonia nitrogen is 52%, the final effluent still has 10.2mg/L. This is because the removal of ammonia nitrogen was not considered in the secondary treatment, and the ammonia nitrogen in the secondary effluent reached 20.3mg/L. Another reason is that the water temperature is too low. The combined process also has a good removal effect on the total number of bacteria, and the removal rate reaches 61%. This can reduce the subsequent disinfection load and reduce the dosage of disinfectant. In addition, after the secondary effluent was passed through the combination process of biological fast filtration and slow filtration, the odor was also reduced to a considerable extent (because the odor detection is highly subjective, no data is given in Table 2).

Table 2 The removal effect of biological fast filtration and slow filtration combined process on main pollutants in winter

Claims (1)

1. biological rapid filtration and slow filtration sewage recycling process for combination, it is characterized in that: comprise biological fast filter and filter step slowly, biological fast filter of this technology utilization and the combination of filter slowly, realize the removal of secondary effluent residual organic substances, ammonia nitrogen, total nitrogen, suspended substance, turbidity, colourity and stink, its concrete steps are as follows: at first, water outlet after the employing sewage second-level is handled is as water inlet, water inlet directly enters biological rapid filter, biological rapid filter has biological action and physical filtering effect simultaneously, in order to remove organism, ammonia nitrogen and the suspended substance in the sewage second-level treat effluent; Then, the water outlet of biological rapid filter enters the slow filter once more, the slow filter relies on the biological action of one deck adhesive film on filtrate top layer further to remove organism, ammonia nitrogen, suspended substance and turbidity material remaining in the biological rapid filter water outlet, simultaneously, utilize the good biofiltration performance in slow filter, remove colourity, stink and bacterium in the water, reach the purpose that improves effluent quality; Sewage is afterwards filtered and filtered slowly to the process biology soon at last, after sterilization, become qualified reuse water, as the greening or the municipal miscellaneous water of flushing the toilet, adopt activated sludge process or bio membrane process to carry out sewage second-level and handle, and whether the purposes decision of looking reuse water carries out denitrogenation dephosphorizing in sewage second-level is handled; Biological filter in the biofiltration step is a conventional rapid filter of having strengthened biological action, biological action wherein relies on following approach to be strengthened: according to the raw water quality situation, the bottom, filter tank is set up aerating apparatus or is carried out preaeration, adjust the filter back washing strategy, reduce back flushing to biomembranous destruction on the filtrate, biological rapid filter water inlet does not add sterilizing agent; According to filtrate, filter bed thickness and influent quality situation, the filtering velocity of biological rapid filter is controlled between 0.5～10m/h; Described biological rapid filter is BAF, bioactivity filter or good air filter pond; Described slow filter has biological action and filteration, and the slow filter does not need back flushing, but need periodically strike-off; According to the influent quality situation, the filtering velocity of slow filter is controlled between 0.1～0.5m/h; Slow filtrate adopts chlorine, ultraviolet ray, dioxide peroxide or ozonation process to carry out disinfection.